1. Field of the Invention
The present invention relates generally to a system and method for selecting an internal parameter value or feature in a power converter, and relates more specifically to selecting an internal parameter value or feature by comparing a programmable reference signal on a multifunction pin to one or more threshold levels.
2. Description of Related Art
Power converters have become more flexible in providing functionality and features in recent years. One reason for advances in power converters is the design flexibility permitted by digital/analog hybrid controllers. These controllers can measure analog signals and perform digital logic and control functions to provide a wide range of features and functionality in realizing a power converter control.
Among the various parameters that influence power converter control is overcurrent detection and response. A popular technique for detecting and responding to an overcurrent condition involves the use of a current limit threshold, where an overcurrent event causes a power controller to register a current related parameter going beyond a threshold. Due to the importance of providing flexibility in setting an overcurrent threshold level, a dedicated pin or connection for the power controller is typically used. A power converter designer typically specifies a passive component for connection to the dedicated pin to achieve an overcurrent threshold setting for the power converter. Typically, the passive component is a resistor that sets or selects a current threshold level that can be compared against a value representative of current flowing through a power stage of the power converter.
If an external component and dedicated pin are not used to set, or program, the overcurrent threshold limit, an internal overcurrent threshold limit is used, which is typically not programmable. Accordingly, flexibility in the design of the power converter is limited. While it is possible to select from multiple controller models that offer various internal overcurrent thresholds, such a power converter design can be inefficient and costly in practice.
It would be desirable to provide a means for permitting a user to select an internal parameter value, in this example an overcurrent threshold, using one controller design, without having to dedicate a controller connection for that purpose.